Bunashimeji mushroom named ‘HKHM25’

ABSTRACT

The present variety of Bunashimeji mushroom named ‘HKHM25’ was cultivated by the gathering and repeated breeding of Bunashimeji mushrooms having thick and elastic stems, dark cap color, strong cap roll, and a large mushroom size, has a high quality and enhanced cultivation stability. This edible mushroom is exquisite in stability, reproducibility and uniformity when being produced.

BACKGROUND OF THE INVENTION

This invention relates to a new and distinct variety of Bunashimeji mushroom, Hypsizygus marmoreus (Peck) H.E.Bigelow. This new variety named ‘HKHM25’, cultivated by repeated breeding of Bunashimeji mushroom having thick and elastic stems, dark cap color, strong cap roll, and a large mushroom size, has a high quality and enhanced cultivation stability, and ensures presentable stability, reproducibility, and uniformity.

The annual production of Bunashimeji mushrooms is approximately 120,000 tons in 2020, making it the second most consumed edible mushroom after enokitake mushroom in Japan. However, since Bunashimeji mushrooms have become available in large quantities in the market, Bunashimeji mushrooms with improved flavor, quality and shelf life has been pursued, which led to the development of ‘Hokuto 18gokin’ by our company. Further, our company has been conducting a wide variety of studies for the more stable cultivation and better quality of Bunashimeji mushrooms. Our company has developed a ‘marmo22go’ mushroom which is thicker, whiter, and has larger mushroom than ‘Hokuto 18gokin’.

Further, using ‘marmo22go’ as a parent, as a result of continuing breed improvement by cross breeding to improve stability and quality, ‘HKHM25’, which has thicker stems and stronger cap roll, as compared to ‘marmo22go’, was developed, confirming its stability, reproducibility, and uniformity.

SUMMARY OF THE INVENTION

The present invention is a new and distinct variety of mushroom plant characterized particularly by having thick and elastic stems, dark cap color, strong cap roll, and a large mushroom size, which can be cultivated by gathering and repeated breeding of fungal strains having a stability, reproducibility and uniformity when being produced. This novel and distinct variety of mushroom is identified as ‘HKHM25’.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a phylogenetic tree illustrating the antecedents of ‘HKHM25’.

FIGS. 2A and 2B respectively show front and back images of a dual-culture of ‘HKHM25’.

FIGS. 3A and 3B respectively show front and back images of a dual-culture of ‘HKHM25’ and ‘Hokuto 18gokin’.

FIGS. 4A and 4B respectively show front and back images of a dual-culture of ‘HKHM25’ and ‘marmo22go’.

FIGS. 5A and 5B respectively show front and back images of a fungal flora of ‘HKHM25’ grown in a petri dish.

FIGS. 6A and 6B respectively show front and back image of a fungal flora of ‘Hokuto 18gokin’ grown in a petri dish.

FIGS. 7A and 7B respectively show front and back images of fungal flora of ‘marmo22go’ grown in a petri dish.

FIG. 8 shows an image of cultivation area of ‘HKHM25’.

FIG. 9 shows an image of cultivation area of ‘Hokuto 18gokin’.

FIG. 10 shows an image of cultivation area of ‘marmo22go’.

FIG. 11 shows an image of a fruit body of ‘HKHM25’.

FIG. 12 shows an image of a fruit body of ‘Hokuto 18gokin’.

FIG. 13 : shows an image of a fruit body of ‘marmo22go’.

FIG. 14 shows an image of density and surface color of fungal flora in cultured hyphae of ‘HKHM25’.

FIG. 15 shows an image of density and surface color of fungal flora in cultured hyphae of ‘Hokuto 18gokin’.

FIG. 16 shows an image of density and surface color of fungal flora in cultured hyphae of ‘marmo22go’.

FIG. 17 shows an image of development of aerial hypha of ‘HKHM25’.

FIG. 18 shows an image of development of aerial hypha of ‘Hokuto 18gokin’.

FIG. 19 shows an image of development of aerial hypha of ‘marmo22go’.

FIG. 20 shows an image of size and distribution of mottle of ‘HKHM25’.

FIG. 21 shows an image of size and distribution of mottle of ‘Hokuto 18gokin’.

FIG. 22 shows an image of size and distribution of mottle of ‘marmo22go’.

FIG. 23 shows an image of shape and thickness of stipe of ‘HKHM25’.

FIG. 24 shows an image of shape and thickness of stipe of ‘Hokuto 18gokin’.

FIG. 25 shows an image of shape and thickness of stipe of ‘marmo22go’.

DETAILED DESCRIPTION OF THE INVENTION

‘HKHM25’ has been asexually reproduced by tissue culture, at HOKUTO CORPORATION in Japan. The history of the ‘HKHM25’ mushroom in terms of improvement period and the like are set forth in the following chronological list of each stage of variety improvement:

-   -   December 2014: Cultivation of ‘MH025615’ strain.     -   January 2017: Cultivation of ‘M11025617’ (‘marmo22go’) strain.     -   December 2019: ‘MH025615’ and ‘MH025617’ (‘marmo22go’) strains         were crossed and a strain with thick stem, strong cap roll, and         good quality among the obtained strains was selected as         ‘MH025633’. We then repeated the cultivation test to distinguish         the strains.     -   March 2021: After repeated cultivation tests, since         distinguishability, stability, and uniformity were confirmed,         the strain was named ‘HKHM25’ and its cultivation was completed.         Applied for registration of a new variety to the Ministry of         Agriculture, Forestry and Fisheries of Japan.

The above crossing is summarized in the phylogenetic tree illustrated in FIG. 1 .

The ‘HKHM25’ mushroom has the following characteristics: thick and elastic stems, dark cap color, strong cap roll, and overall large size.

(1) Comparison with Existing Variety by Dual Culture

Dual culture was performed for the ‘HKHM25’ mushroom and a similar variety to examine whether or not a zone line is formed.

Study Method:

As an examination method, a potato dextrose agar medium was used, and the ‘HKHM25’ mushroom and the similar variety were inoculated thereon face to face at an interval of 3 cm, and then culture was performed at 25° C. for 28 days to examine whether or not a zone line was formed.

Strains used for the comparison between present variety, ‘HKHM25’ and other varieties:

-   -   ‘HKHM25’: Present variety     -   ‘Hokuto 18gokin’: Variety similar to the present variety     -   ‘marmo22go’: Parent variety of the present variety         Results:

Zone lines were formed between ‘HKHM25’ and all other co-cultured varieties

(TABLE 1, FIGS. 2 to 4) This clearly shows that the present mushroom is a new variety. Similar varieties Hokuto 18gokin marmo22go HKHM25 + + + is present and − is absent. *Zone line formation was not observed in the dual culture between ‘HKHM25’ strains. (2) Growth Characteristics of ‘HKHM25’ Study Method:

After inoculating an agar piece of the ‘HKHM25’ having a diameter of 5 mm and an agar piece of the similar variety having a diameter of 5 mm on a potato dextrose agar medium, preculture was performed at 25° C. for 4 days so as to make the regeneration of hyphae equal (about 10 mm in diameter), and then culture was performed for 7 days at intervals of 5° C. between 5° C. and 30° C. An average daily hyphae growth rate was calculated based on a hyphae growth rate for 7 days of the culture. Also, the optimum culture period for ‘HKHM25’ is 80 days, and the number of growing days at that time is 23.1 days.

Results:

‘HKHM25’ had the fastest average daily hyphae growth rate at 20° C. In addition, HKHM25 had slower mycelial growth rate than ‘Hokuto 18gokin’ and ‘marmo22go’ at each temperature zone (Table 2).

(3) Morphological Characteristics of the ‘HKHM25’ Mushroom in a Cultivation Example

Cultivation Method:

Container: An 850 polypropylene bottle (Capacity: 850 ml, diameter 58 mm) was used.

Culture medium: Conifer sawdust, corn cob, rice bran and wheat bran were mixed at the dry weight ratio of 7:3:8:2, and the water content was adjusted to 65%. The culture medium was filled up to the brim of the bottle at the rate of 540±20 g per bottle, and was sterilized at high pressure.

Starter culture: About 20 ml of sawdust starter cultures per bottle was inoculated.

Culture: Culture was performed at 22° C. for 50 to 90 days at 70% moisture.

Growth: After completing the culture, the inoculum is removed, and shifted to a growing room. Development was conducted under a temperature of 15±1° C., at humidity of 95% or about 2,000 ppm CO₂ density. Also, light was not particularly irradiated until the first 14th day, then irradiated with about 500 to 1,000 Lx. The mushroom is harvested when the cap in the center of the stump has sufficiently opened.

Cultivation Results:

Table 2 shows the characteristics of the ‘HKHM25’ and specific difference in characteristics as compared with the similar variety when culture was performed under the abovementioned conditions.

In addition, according to R.H.S. Colour Chart, the color of the central part of cap: 199A, the color of the peripheral area of cap: 199C, the color of gill: 158C, the color of stripe: 155B. All color references are from The R.H.S. Colour Chart of The Royal Horticultural Society of London (R.H.S.), fifth edition published in 2007. Also, the descriptions are from mushrooms that are on the 24^(th) day.

TABLE 2 Fungus characteristics Table of Hypsizygus marmoreus (Peck) H.E. Bigelow of Recording and Registration (Please circle the applicable items for the characteristics.) Characteristic values Remarks of similar Characteristic values of present variety (comparison (Measured varieties with standard varieties values, (Hokuto Character 01 02 03 04 05 06 07 08 09 etc.) (marmo22go) 18gokin) Physio- logical property Dual culture Zone line none ob- — 09 09 formation served Dislike- none ob- — 01 01 touch served reaction Density of cultured hyphae low medium

03 02 02 Develop- ment of aerial low medium

03 03 02 hypha Color of surface of fungal flora white

pale yellow other 02 01 01 Color of back of fungal flora white

pale yellow other 02 02 02 Accommo- dativeness for temperature Optimal temperature for hyphal growth

24~ 26° C. 28~ 30° C. 03 21.9° C. 05 24.1° C. 04 22.5° C. Hyphal growth rate 5° C./mm low

high 05 0.52 mm 06 0.70 mm 05 0.56 mm Hyphal growth rate 10° C./mm low

medium 04 0.86 mm 05 1.16 mm 05 1.24 mm 15° C./mm low

high 05 1.65 mm 05 1.95 mm 05 1.80 mm 20° C./mm low

medium high 04 2.47 mm 05 2.79 mm 05 2.60 mm 25° C./mm low

medium high 04 2.01 mm 05 3.29 mm 04 2.47 mm 30° C./mm low

medium high 04 0.91 mm 07 2.17 mm 05 1.23 mm Morpho- logical property Cap Cross sectional shape convex

flat con- cave other 02 02 02 Mottle of the surface few

many 02 02 02 Size of mottle small medium

03 01 03 Distribution of mottle

whole part 01 02 02 Clarity of mottle unclarity moderate

03 03 03 Size

medium large 03 21.2 mm 03 23.2 mm 02 20.4 mm Color of central area white grey- yellow light grey- brown yellow- brown

dark tan dark grey tan dark grey brown other 05 199A 05 199C 05 199B Color of peripheral area white grey- yellow light grey- brown yellow- brown

dark tan dark grey tan dark grey brown other 05 199C 05 199D 05 199D Thickness thin medium thick

08 9.8 mm 09 11.3 mm 0.7 8.1 mm Fleshy soft

hard 05 05 07 Gill Color white

light orange yellow grey- yellow other 02 158C 02 158C 02 158C Alignment normal

other 02 02 02 Width narrow

wide 02 02 02 Density low

high 02 02 02 Stipe Shape long and thin short and thin long and thick short and thick

05 05 01 Length short

long 05 56.0 mm 05 53.9 mm 04 52.8 mm Thickness thin medium thick

09 17.7 mm 08 16.5 mm 05 9.4 mm Color

yellow- white grey grey- brown other 01 155B 01 155B 01 155B Hair

few medium many 01 01 01 Fleshy soft medium

03 02 02 Ratio of maximum diameter of small medium

07 2.24 06 1.91 04 1.52 stem to diameter just below cap Cultural property Develop- ment of fruit body Develop- ment group scattered

03 03 03 Optimal culture period short

long 05 80 days 05 80 days 06 90 days Length of time from fruit body- short

long 05 23.3 days 04 21.9 days 05 22.3 days formation promotion to fruit body harvesting Optimal temperature for low medium

07 19° C. 07 19° C. 05 15° C. primordial development Optimal temperature for fruit body low

high 05 15° C. 05 15° C. 05 15° C. growth Adaptivity for illuminance Adaptivity for culture Yield Yield of fruit body few

many 05 125.4 g 06 137.0 g 02 98.4 g The number of productive

few medium many 02 19.4 stems 03 21.7 stems 03 23.6 stems stems Other property Bitter none weak strong ingredient Disease resistance Ingredients Notes: Circle shows the characteristics of ‘HKHM25’. The R.H.S. Colour Chart of The Royal Horticultural Society of London (R.H.S.), fifth edition published in 2007, The R.H.S. contact: R.H.S. Membership Department The Royal Horticultural Society PO Box 313 London, SW1P 2PE 

What is claimed is:
 1. A new, distinct variety of Bunashimeji Mushroom as substantially illustrated and described in the specification. 